"They are probably effective, but they can cause harm and most patients will get better without them.

"Antibiotics should only be used when symptoms have persisted for long enough to concern parents of patients."

Side-effects

The study found that antibiotics can often have side-effects, including vomiting, diarrhoea and abdominal pain.

However, Dr Jim Kennedy, prescribing spokesman for the Royal College of GPs, said it was very unusual for family doctors in the UK to prescribe antibiotics for a runny nose - only about 1 in 100 patients would get such drugs.

"There are only a few cases where most GPs would even consider prescribing antibiotics. If a patients has a history of bronchitis and sinusitis.

"The best advice to give is to keep blowing your nose to get rid of the virus.

"If antibiotics are overused as well as possible side-effects, there is a risk that we will encourage resistance."